How does no one know!?

i've asked a ton of people what the number means on the back of practically any cosmetic product with the capitol M next to it. No one has ever been able to answer me, what is it?? On my OPI nail polish it's either 24M or 36M and on Bare Escentuals powder foundation it's 12 as is Tarte lip stain

Re: How does no one know!?

This is called a PAO symbol, or "period after opening" -- meaning how long the manufacturer suggests the is product viable after opening it initially. The M stands for months -- i.e., 6M (6 months), 24M, 36M, etc. For some cosmetic products, like mascara, the life span will be shorter -- such as 3M or 6M, and you generally want to pay attention to those, or any liquid-based product like foundation -- because these will eventually go bad. In addition to using the PAO symbol as a guideline, you can also judge by the product itself -- if it changes consistency, starts to smell, separates, etc. -- toss it, no matter what the symbol says. However, I will say that powder-based products -- like eyeshadow or blush -- will keep for much longer than their cited period (usually around 24M) if you take good care of them (clean them, don't store them in the bathroom or a humid area, etc.).